<?php
//**************************************************************************
//
//            (C) Okulov Rostislav, 2011
//
//**************************************************************************

/*
 ***************************************************************************
 *                                                                         *
 *   This source is free software; you can redistribute it and/or modify   *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This code is distributed in the hope that it will be useful, but      *
 *   WITHOUT ANY WARRANTY; without even the implied warranty of            *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU     *
 *   General Public License for more details.                              *
 *                                                                         *
 *   A copy of the GNU General Public License is available on the World    *
 *   Wide Web at <http://www.gnu.org/copyleft/gpl.html>. You can also      *
 *   obtain it by writing to the Free Software Foundation,                 *
 *   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.        *
 *                                                                         *
 */

 if (preg_match("/^[\s]?[0-9]+[\s]?(\*|\+|\-|\/)[\s]?[0-9]+[\s]?$/", $_POST['send'])) { 
 // в выражении разрешим поставить по одному пробелу с каждой стороны.

         preg_match("/\*|\+|\-|\//", $_POST['send'], $matches);
         $return_vals = preg_split("/\*|\+|\-|\//", $_POST['send']);

         $return_vals[0] = trim($return_vals[0]); // уберем пробелы если таковые имеются на таб^Wесть в строке.
         $return_vals[1] = trim($return_vals[1]);

         // что там у нас за арифметический знак?
         switch ($matches[0]) {
         case '+':
             echo $return_vals[0] + $return_vals[1];
             break;
         case '-':
             echo $return_vals[0] - $return_vals[1];
             break;
         case '*':
             echo $return_vals[0] * $return_vals[1];
             break;
         case '/':
             echo $return_vals[0] / $return_vals[1];
             break;
         }

 }
 else 
 {
         echo 'bad string'; // очень плохая строка, возможно пытаются подсунуть какую-нибудь гадость...
 }
?>
